The present invention relates to a storage system, and more particularly to a disk array system having a plurality of disk array control units.
As the capacity of storage systems increases, there are cases where many volumes which were dispersed conventionally are handled as one storage to integrate the storage system. In such cases, volumes with various access patterns are mixed within a single storage system. Thus, accesses may concentrate on a specific volume, and that volume must be capable of high-level performance.
A method has been proposed, which is used for taking over the volumes between controllers to reduce the load. Specifically, a disk array system is proposed in which a switch-source controller writes data from the relevant volume in a data cache onto a disk and the coherence of the disk is preserved. Accordingly, even in a case where each controller is provided with an independent dedicated cache, any volume area can be taken over by any controller, without interrupting the system. (refer to JP 2003-162377